Cumulative trauma disorders are a major health problem among workers in some manual industries. The purpose of this work is to investigate how handle design affects stresses in the worker's hand. It is hypothesized that handle vibration, temperature, and hardness affect the onset of temporary numbness and the tonic vibration reflex for inexperienced operators. This results in the application of excessive hand grip force which contributes to the incidence of cumulative trauma disorders. Laboratory subjects will hold a handle-shaker assembly which is equipped with a strain gauge hand dynomonometer. The onset of temporary numbness will be measureed using objective tactility tests, such as two point discrimination, light tough to deep pressure identification and pick up tests, at intervals after vibration exposure. Presence of the tonic vibration reflex will be indicated by electromyographic activity correlated with the vibration stimuli. The relationship between handle hardness, temperature and vibration on hand grip force will be determined. A cross sectional study of the hand grip forces exerted by workers with varying experience operating hand tools will be made and the results obtained in the laboratory will be verified in the field.